Molybdenum (Mo) crucibles find widespread use in the production of sapphire single crystals due to their beneficial refractory properties, including a high melting point. Most Mo crucibles are fabricated either by the deep drawing of Mo sheets or via powder metallurgy techniques utilizing high-purity Mo powder. However, such techniques are often difficult and expensive to implement. For example, the powder metallurgy of Mo typically requires expensive, high-purity Mo powder. Furthermore, the powder-metallurgy processing of Mo powder generally results in Mo crucibles with densities less than 100%, which may compromise the mechanical properties (e.g., toughness) of such crucibles.
Furthermore, while Mo crucibles may be suitable for many sapphire fabrication processes, pure Mo tends to have a relatively high vapor pressure, which may result in contamination as the sapphire is grown from the liquid melt. While crucibles made of tungsten (W) or even uniform Mo—W alloys (e.g., formed by powder metallurgy of mixed Mo and W powders) can alleviate some of the issues arising from the use of pure Mo crucibles, such crucibles tend to be heavy (and thus difficult to handle), quite expensive, and generally have lower toughness (particularly in the case of pure W).
In view of the foregoing, there is a need for techniques not only for the more efficient production of refractory metal (e.g., Mo) crucibles, but also for crucibles incorporating the advantageous properties of refractory metal alloys (e.g., Mo—W alloys) without the above-described disadvantages.